1. Field of the Invention
The present invention generally relates to processes for transforming 1,2-diols into olefins, and more particularly to processes for preparing nucleoside derivatives.
2. Discussion of the Background
To convert compounds of formula (I) ##STR3## into the 2',3'-didehydro-2',3'-dideoxynucleoside derivatives of formula (III) ##STR4## which are important intermediates for preparing pharmaceutically active substances such as antiviral agents, the following known methods can be used:
(1) a method using Zn--AcOH (M. J. Robins et al., Tetrahedron Lett., 25, 367 (1984); B. Samuelsson et al., Acta Chem. Scand., B36, 215 (1982); J. Chattopadhyaya et al., Acta Chem. Scand., B40, 251 (1982));
(2) a method using Cr(OAc).sub.2 en.sub.2 (T. C. Jain et al., J. Org. Chem., 39, 30 (1974));
(3) a method using electrode mediated reduction (T. Adachi et al., J. Org. Chem., 44, 1404 (1979)); etc.
With method (1), it is difficult to remove the zinc complexes from the reaction mixture. With method (2) it is difficult to prepare the reactants used and several by-products are formed due to the difficult separation operations used therein. Method (3) suffers the problem that a special reaction device is required.
There is thus a need for a better process for preparing the compounds of formula (III) from compounds of formula (I).